1. Field of Art
The present invention relates to a process for producing biphenyl derivatives. More particularly, the present invention relates to a process for producing biphenyl deviatives which is characterized in that a biphenyl skeleton is formed by the dehydrogenation of a cyclohexylbenzene structure.
More specifically, the present invention relates, in one embodiment thereof to a process for producing 4-biphenylylacetic acid derivatives or intermediates thereof which are useful, for example, as anti-inflammatory, analgesic and antipyretic agents.
2. Prior Art
Generally, the introduction of a substituent into a specific position of a biphenyl derivative or the synthesis of a biphenyl derivative having a substituent at a specific position is often difficult depending upon the position into which the substituent is introduced.
For example, with regard to the synthesis of a biphenyl skeleton of 4-biphenylylacetic acids including .alpha.-methyl-(2-fluoro-4-biphenylyl)acetic acid which is a particularly well-known anti-inflammatory agent among the above mentioned 4-biphenylylacetic acid derivatives, Japanese Patent Publication No. 28369/1970 discloses, as a process for synthesizing biphenyl derivatives whose intermediates have a predetermined position for a substituent, an Ullmann's condensation process wherein a bromobenzene derivative is reacted with an equimolar or more of iodobenzene and metallic copper and a diazophenylation process wherein an aniline derivative is subjected to diazotization, and the resulting diazo compound is reacted with benzene.
However, the former process is accompanied by a problem in that iodobenzene, which is expensive, is used in an excessive amount and iodobenzene or the starting material is inevitably condensed with each other due to the cross condensation reaction. On the other hand, the latter process involving the diazotization is accompanied by a problem in that the synthesis of the starting aniline derivative is difficult depending upon the position of the substituent of the intended compound. Further, it cannot but the said that the yield of the diazophenylation reaction is low.